I searched here wow and here whoa and they seem to be pronounced differently. I'm concerned only when the meaning is to signify surprise. However, I'm not sure when to use one or anotherthe other,since since both seem to express surprise. Seems to me "wow" is for mostly positive surprise (although could be used ironically) and whoa"whoa" for negative connotation. My question is specific to the US to make it more answerable and because I'm interested in that case.